Fluid couplings for belt
conveyors
Voith recently manufactured its 1000
th
TPKL
fluid coupling (Figure 1). The production of
the series, especially developed for mining
applications, started in 1997. It is suitable for
long conveyor types, heavy-duty, high-
inertia systems, with demanding start-up
conditions and complex conveyor layouts.
The coupling provides excellent torque
limitation, 120% of the nominal load and
start-up times of up to several minutes.
The pre-tensioning and start-up time
can be varied according to customer
requirements. With the Voith TurboSim
software start-up procedures can be
calculated taking into consideration
various parameters: for example, start-up
scenario, load situations and ambient
conditions, as well as interactions with
other components. Figure 2 illustrates the
pre-tensioning and soft acceleration of a
belt conveyor in a Mozambican coal mine.
The customer requested a start-up time of
190 sec. for the belt conveyor. A 250 kW
motor running at 1490 rpm and a 562
TPKL fluid coupling are used. The start-up
procedure is as follows. The motor starts
up virtually load-free as the coupling is
empty. By filling the coupling, torque is
increasing smoothly and the belt is
pre-tensioned (approximately 10 sec.).
This reduces dynamics in the belt and
avoids longitudinal vibrations. Through
filling control, the belt accelerates (yellow
curve). The TPKL fluid coupling limits the
introduced torque to 120% of the load
torque (blue curves). After 190 sec., the
belt conveyor has reached nominal
operation.
The belt pre-tensioning, as well as soft
and controlled acceleration of the belt
conveyor, avoids damages on the belt and
increases its lifetime. The TPKL comes with
an active cooling function (Figure 3), so it
can handle the most demanding start-up
procedures multiple times in succession. For
belt inspection, the coupling can be operated
with partial filling – the belt conveyor runs
at reduced speed.
The heat, which is produced by
extended start-up times or long‑term
reduced speed operation, is generated
directly in the operating medium (oil) and is
quickly dissipated by a heat exchanger that
is integrated in the coupling circuit. This
involves the operating fluid recirculating
continuously during operation in a closed
Figure 2. Start-up of a Mozambican coal mine.
Figure 1. The TPKL fluid coupling is ideally suited for use in belt conveyor drives
with challenging workloads.
38
|
World Coal
|
January 2016
